How to search text surrounded by double-quotes with RegEx?

Question

I have a string with some HTML code in, for example:

This is <strong id="c1-id-8">some</strong> <em id="c1-id-9">text</em>

I need to strip out the id attribute from every HTML tag, but I have zero experience with regular expressions, so I searched here and there from the internet and I wrote this pattern: [\s]+id=\".*\"

Unfortunately it's not working as I would expect. Infact, I was hoping that the regular expression would catch the id=" followed by any character repeated for any number of times and terminated with the nearest double quote; Practically in this example I was expecting to catch id="c1-id-8" and id="c1-id-9". But instead the pattern returned me the substring id="c1-id-8">some</strong> <em id="c1-id-9", it finds the first occurrence of id=" and the last occurrence of a double quote character.

Could you tell me what is wrong in my pattern and how to fix it, please? Thank you very much

Answer 1

The quantifier .* in your regex is greedy (meaning it matches as much as it can). In order to match the minimum required you could use something like /\s+id=\"[^\"]*\"/. The brackets [] indicate a character class. So it will match everything inside of the brackets. The carat [^] at the beginning of your character class is a negation, meaning it will match everything except what is specified in the brackets.

An alternative would be to tell the .* quantifier to be lazy by changing it to .*? which will match as little as it can.

Answer 2

In .* the asterisk is a greedy quantifier and matches as many characters as it can, so it only stops at the last " it finds.

You can either use ".*?" to make it lazy, or (better IMO), use "[^"]*" to make the match explicit:

"      # match a quote
[^"]*  # match any number of characters except quotes
"      # match a quote

You might still need to escape the quotes if you're building the regex from a string; otherwise that's not necessary since quotes are no special characters in a regex.